CN101628242A - Molecular sieve catalyst for preparing low-carbon olefin and preparation method thereof - Google Patents

Abstract

The invention provides a molecular sieve catalyst for preparing low-carbon olefins. In parts by weight, the catalyst is made of raw materials comprising the following components: 30-93.7 parts of sodium ZSM-5 zeolite, 5-40 parts of Adhesive, 0.1-10 parts of heteroelement modifier, 1-15 parts of pore structure modifier and 0.1-5 parts of extrusion aid, and the heteroelement modifier contains B, P, La , Ca, Mg, Sr, Zn, Cu, Mn, Cd, Ga and In the soluble matter of one or more elements. The invention also provides a preparation method of the catalyst. In the present invention, the extrusion aid is used and an appropriate amount of pore structure regulator is added to improve the strength and pore structure of the product, effectively improve the diffusion performance of the catalyst, and thereby increase the selectivity of low-carbon olefins. The catalyst of the invention has suitable strength and high hydrothermal stability, and exhibits high activity and selectivity to propylene.

Description

A molecular sieve catalyst for preparing low-carbon olefins and its preparation method

technical field

The invention relates to a molecular sieve catalyst for preparing low-carbon olefins and a preparation method of the catalyst, in particular, the present invention relates to a shaped molecular sieve catalyst for converting methanol and/or dimethyl ether into low-carbon olefins and the preparation of the catalyst The preparation method belongs to the field of coal chemical industry.

Background technique

Low-carbon olefins are the most basic raw materials for petrochemical production and the basis for the production of other chemical products. At present, the production of low-carbon olefins is mainly based on petroleum routes and non-petroleum routes. The production of low-carbon olefins (methanol-to-olefins, MTO) such as ethylene and propylene from coal or natural gas via methanol and/or dimethyl ether is the most important non-petroleum resource technology route. In recent years, due to the rising oil price and the rapid growth of propylene demand, the conversion of methanol to propylene (methanol-to-propylene, MTP) using methanol as raw material has attracted more and more attention.

In the prior art, the fixed-bed MTP process and the ZSM-5 catalyst in the process are disclosed. However, these current catalysts generally have the disadvantages of low propylene selectivity, poor catalyst stability, and decreased propylene selectivity after molding.

Therefore, there is a need for a catalyst that can increase the yield of olefins and has stability.

Contents of the invention

To facilitate understanding of the present invention, some terms are defined below. Terms defined herein have meanings commonly understood by those of ordinary skill in the art to which the present invention pertains.

Unless otherwise stated, "precursor" herein refers to a precursor that undergoes some manipulation steps or reaction steps to produce the target product.

Unless otherwise specified, "sodium ZSM-5 zeolite" in this article refers to a synthetic mesoporous five-membered ring zeolite with a three-dimensional pore structure, that is, molecular sieve, which is a kind of silicon-aluminum ratio that can be used in a wide range. The internally modified powdery porous aluminosilicate crystalline material, the unit cell composition of which can be expressed as Na _n Al _n Si _96-n O ₁₉₂ ·16H ₂ O, n<27.

Unless otherwise specified, the "heteroelement modifier" in this paper refers to the one or more elements containing B, P, La, Ca, Mg, Sr, Zn, Cu, Mn, Cd, Ga and In Soluble matter, because the above-mentioned elements do not exist in the sodium ZSM-5 zeolite of the catalyst, so it can play a role in improving the properties of the catalyst.

Unless otherwise specified, the "pore structure modifier" herein refers to a substance that can improve the pore structure of a catalyst.

Unless otherwise specified, the "extrusion aid" herein refers to the raw material required to help the catalyst raw material pass through the molding operation in the preparation of the catalyst.

Unless otherwise specified, the "peptizer" herein refers to a substance that needs to be added during the forming process of the catalyst to increase the cohesiveness between the particles of the raw material, so as to increase the strength of the catalyst and improve the pore structure of the catalyst.

An object of the present invention is to provide a molecular sieve catalyst for preparing light olefins. The catalyst is used in the reaction of preparing light olefins from methanol and/or dimethyl ether, and in the reaction, the catalyst has high mechanical strength, high thermal stability and high selectivity of propylene.

Another object of the present invention is also to provide the preparation method of this catalyst.

For the above purpose, the present invention provides a molecular sieve catalyst for preparing low-carbon olefins, in parts by weight, the catalyst is made of raw materials comprising the following components: 30-93.7 parts of sodium ZSM-5 zeolite , 5-40 parts of binder, 0.1-10 parts of heteroelement modifier, 1-15 parts of pore structure regulator and 0.1-5 parts of extrusion aid, and the heteroelement modifier is Soluble substances containing one or several elements of B, P, La, Ca, Mg, Sr, Zn, Cu, Mn, Cd, Ga and In.

Preferably, in parts by weight, each component in the raw material is: 46-87.2 parts of sodium ZSM-5 zeolite, 10-30 parts of binder, 0.5-5 parts of heteroelement modifier, 2 - 7 parts of pore structure regulator and 0.3-2 parts of extrusion aid.

Preferably, the sodium ZSM-5 zeolite is a sodium ZSM-5 zeolite with a silica aluminum molar ratio (SAR) of 20-2000.

More preferably, the sodium ZSM-5 zeolite is a sodium ZSM-5 zeolite with a particle size of 0.1 mm or less and a silicon-aluminum molar ratio of 200-1000.

Preferably, the binder is selected from one or more of aluminum hydroxide, activated alumina, boehmite, pseudo-boehmite, silica sol and clay with a particle size of less than 0.1 mm.

Preferably, the binder is selected from one or more of activated alumina, pseudoboehmite, silica sol and clay.

Preferably, the pore structure regulator is selected from one or more of methylcellulose, starch, polyvinyl alcohol, polyethylene glycol, sucrose and glucose.

Preferably, the pore regulator is selected from one or more of methylcellulose, starch and sucrose.

Preferably, the extrusion aid is selected from one or more of graphite powder, turnip powder, oxalic acid, tartaric acid, citric acid, glycerin and stearic acid.

Preferably, the extrusion aid is an extrusion aid composed of any two of turnip powder, citric acid and glycerin in a mass ratio of 1:1.

Preferably, the heteroelement modifier is a soluble substance containing one or more elements among P, Mg, La, Mn and Zn.

The present invention also provides a kind of method for preparing described molecular sieve catalyst on the other hand, this method comprises the following steps:

a. mix sodium type ZSM-5 zeolite, pore structure regulator, extrusion aid, binder, heteroelement modifier and peptizer evenly;

b. molding the mixture obtained in step a, drying, and calcining to obtain the precursor I of the catalyst;

c. exchange the precursor I of the catalyst obtained in step b in 1) one or more solutions selected from hydrochloric acid, sulfuric acid and nitric acid or 2) an inorganic ammonium solution, and obtain the catalyst precursor II after drying;

d. Treat the catalyst precursor II obtained in step c with a mixed gas of water vapor and N ₂ to obtain the catalyst. "Shaping" in step b is to make the mixture in step a into a shaped catalyst with a certain shape and size in a molding machine.

Preferably, in the step a, the sodium ZSM-5 zeolite, the pore structure regulator and the extrusion aid are firstly mixed to obtain a mixture, and then the heteroelement modifier and the peptizing agent are added to the mixture. The purpose of adding the peptizer in the method of the present invention is to generate false aluminum sol in the molding process, which can be bonded with the dry glue to facilitate molding.

Preferably, the peptizer is selected from one or more of nitric acid, hydrochloric acid, phosphoric acid, sulfuric acid, formic acid, acetic acid and malonic acid.

More preferably, the peptizer is selected from one or more of nitric acid, acetic acid and phosphoric acid.

Preferably, when the binder in step a is silica sol, step a is uniformly mixing sodium ZSM-5 zeolite, pore structure regulator, extrusion aid and heteroelement modifier.

Preferably, in said step b, the mixture obtained in step a is shaped, dried at 50-120°C, and calcined at 500-700°C for 5-7 hours in an air atmosphere to obtain catalyst precursor I.

More preferably, in step b, the mixture obtained in step a is molded, dried at 70-100° C., and calcined at 550-650° C. for 5-6 hours in an air atmosphere to obtain catalyst precursor I.

Most preferably, in step b, the mixture obtained in step a is molded, dried at a constant temperature of 80° C., and calcined at 600° C. for 5 hours in an air atmosphere to obtain catalyst precursor I.

Preferably, wherein in said step c, the precursor I of the catalyst obtained in step b is in 1) one or more solutions selected from hydrochloric acid, sulfuric acid and nitric acid with a mass percentage content of 0.1-5% Or 2) one or more solutions selected from ammonium nitrate, ammonium chloride and ammonium bicarbonate with a mass percentage of 0.1-5% are exchanged 2-5 times at 20-90°C, each time for 1-6 hours , and then wash the exchanged catalyst precursor I with deionized water, and then dry the catalyst precursor I at 60-160° C. to obtain the catalyst precursor II.

More preferably, the precursor I of the catalyst obtained in step b is exchanged 3-4 times at 40-70° C. in one or more solutions selected from hydrochloric acid, sulfuric acid and nitric acid with a mass percentage content of 0.8-4%. , each time for 2-5 hours, and then wash the exchanged catalyst precursor I with deionized water, and then dry the catalyst precursor I at 90-140° C. to obtain the catalyst precursor II.

Most preferably, the precursor I of the catalyst obtained in step b is exchanged 3 times at 60° C. for 2 hours each time in 3% by mass percent of one or more solutions selected from hydrochloric acid, sulfuric acid and nitric acid. The exchanged catalyst precursor I was washed with deionized water, and then the catalyst precursor I was dried at 120° C. to obtain the catalyst precursor II.

Preferably, in said step d, the mixed gas of water vapor and N ₂ is treated at 400-700°C for 5-10 hours, and the water vapor accounts for 30-70% of the volume of the mixed gas.

More preferably, in said step d, the mixed gas of water vapor and N ₂ is treated at 500-600° C. for 5-8 hours, and the water vapor accounts for 40-60% of the volume of the mixed gas.

Most preferably, in the step d, the mixed gas of water vapor and N ₂ is treated at 600° C. for 8 hours, and the water vapor accounts for 50% of the volume of the mixed gas.

The catalyst evaluation device of the present invention adopts a fixed-bed flow reactor, and the loading amount of catalyst for each evaluation is 3.0 g, with methanol and/or dimethyl ether as raw material, water as diluent, when CH ₃ OH or CH ₃ OCH ₃ When used as raw materials, the mass ratio CH ₃ OH: H ₂ O = 2: 1 or CH ₃ OCH ₃ : H ₂ O = 2: 1; when using CH ₃ OH and CH ₃ OCH ₃ as raw materials, CH ₃ OH and The ratio of CH ₃ OCH ₃ can be arbitrary, but the mass ratio of the sum of CH ₃ OH and CH ₃ OCH ₃ to water is still (CH ₃ OH+CH ₃ OHOCH ₃ ):H ₂ O=2:1, liquid The hourly space velocity is 1h ^-1 , the reaction temperature is 480°C, and the total system pressure is less than 0.05MPa. The reaction product is analyzed by a hydrogen flame ionization detector (FID). The product selectivity is calculated based on the mass percentage of carbon-based products. . Heteroatoms such as Ca, Mg, Zn, Sr, Cu, Mn, Cd, Ga, In, La, B, and P can significantly inhibit the acidity of molecular sieves or generate acid-base bifunctional sites on the surface of catalysts after entering the structure or surface of molecular sieves. Improve the coking resistance, life and selectivity to lower olefins of sodium ZSM-5 zeolite molecular sieve. The general method of introducing the heteroelement modifier is to modify the former powder of sodium type ZSM-5 zeolite and then shape it or to modify the catalyst first. In the present invention, the introduction of the heteroelement modifier and the catalyst Synchronous molding of the catalyst simplifies the production steps of the catalyst and effectively reduces the production cost of the industrial catalyst. In addition, in the present invention, the use of composite extrusion aids and the addition of an appropriate amount of pore structure regulators can not only make the catalyst easy to demould, but also improve the strength and pore structure of the product, effectively improve the diffusion performance of the catalyst, thereby improving the low-carbon Alkene selectivity. The catalyst of the invention has suitable strength and high hydrothermal stability, and exhibits high activity and selectivity to propylene in methanol and/or dimethyl ether conversion reaction.

Detailed ways

The present invention will be further described below in conjunction with specific examples, but these examples are only limited to explaining the present invention, and are not intended to limit the present invention. The experimental methods of the specific experimental conditions not indicated in the following examples are usually according to conventional conditions, or according to the conditions suggested by the manufacturer, and the changes in the technical solutions in the following examples are all within the protection scope of the present invention.

Example 1

Take 100g of ZSM-5 zeolite raw powder (SAR=200), add 25g of alumina, 2g of methyl cellulose and 3g of scallop powder to it, mix the above raw materials evenly, and adjust the liquid-solid ratio to 1.5mL of nitric acid/2g of zeolite A nitric acid solution with a mass percent content of 20% was used as a peptizer, and 3.4 g of La(NO ₃ ) ₃ ·6H ₂ O heteroelement modifier was added. Other preparation steps were the same as in Comparative Example 1, and the obtained catalyst was marked as S-1, and the catalyst contained 1% La by mass percentage. S-1 was crushed, and 20-40 mesh particles were screened out for activity evaluation. Methanol and water were used as feedstock for the reaction (mass ratio CH ₃ OH:H ₂ O=2:1), and the catalyst activity evaluation results were as follows: Table 1 shows. The results of catalyst activity evaluation are shown in Table 1.

As shown in Table 1, under the same methanol conversion rate, the La modification of ZSM-5 zeolite is beneficial to improve the selectivity of the target product propylene. Compared with the general method of introducing heteroelement modifiers (i.e. first modifying the original powder and then molding or molding the catalyst first and then modifying), the heteroelement modification and molding technology of the present invention are carried out simultaneously Catalyst preparation technology, catalyst strength and selectivity to propylene are significantly improved.

The intensity and the reaction result of the catalyst of Table 1 Comparative Example 1-3 and Embodiment 1

^* is the sum of 1-butene, 2-butene and isobutene

Example 2-11

Weigh 100g of sodium-type ZSM-5 zeolite with SAR of 300, 400, 500, 600 and 700 respectively for molding, add one or several different binders and pore structure regulators, and then add peptizer and heteroelement modification sex agent. The peptizers are respectively nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, formic acid, acetic acid or malonic acid, the amount of which is added according to the liquid-solid ratio of 1.5mL/2g zeolite, the type and concentration of acid used for ion exchange, water vapor concentration and treatment The time is listed in Table 2. The heteroelement modifier is one or more of the soluble precursors containing Mg, P, In, Zn, Cu, Mn, Ga, Sr and Ca. The specific raw material ratio is as shown in Table 2, the other preparation steps of the shaped catalyst are the same as in Example 1. The reaction was fed with mixed feed of dimethyl ether and water (mass ratio CH ₃ OCH ₃ :H ₂ O=2:1), and the activity evaluation results of the catalyst are shown in Table 2.

Raw material ratio and preparation conditions of table 2 embodiment 2-11

Number % by volume) 2 300 Aluminum hydroxide 15g Starch 3.0g Tianjing Powder 4.0g Mg(NO ₃ ) ₂ 6H ₂ O3.1g _HNO3 20% HCl 4% 70% 10h 3 400 Activated alumina 30g Polyvinyl alcohol 5.0g 1.0g lemon and 1.0g sage powder H ₃ PO ₄ 1.8g HCl20% HNO ₃ 3% 60% 8 hours 4 500 Boehmite 20g Methylcellulose 2.0 Oxalic acid 2.6g In(NO ₃ ) ₂ 2.6g _{H3PO4 10} % _{H2SO4 _} 1% 50% 7h 5 600 Pseudoboehmite 15g Methylcellulose 7.0g Tartaric acid 1.5g Zn(NO ₃ ) ₂ ·6H ₂ O10.7g HCOOH40% _HNO3 and HCl Contains 2% _HNO3 and 1% HCl 50% 6 hours 6 600 Aluminum hydroxide 10g and activated alumina 10g Starch 5.0g Glycerin 2.0g Cu(NO ₃ ) ₂ ·3H ₂ O2.9g _HCH3OOH30 % HNO ₃ 1% 50% 6 hours 7 600 Activated alumina 30g and pseudo-boehmite 15g Sucrose 2.0g and starch 3.0g Stearic acid 1.0g Mn(NO ₃ ) ₂ 0.8g and Cu(NO ₃ ) ₂ ·3H ₂ O2.9g _HNO3 20% HNO ₃ 1% 50% 6 hours

8 700 Pseudoboehmite 10g, aluminum hydroxide 10g and activated alumina 10g 5.0g polyethylene glycol, 5.0g polyvinyl alcohol and 2.0g sucrose 3.0g graphite powder and 1.0g safflower powder Ga(NO ₃ ) ₂ ·9H ₂ O3.3g _HNO3 20% HNO ₃ , H ₂ SO ₄ and HCl Contains 1% HNO ₃ , 1% H ₂ SO ₄ and 1% HCl 45% 5h 9 700 Aluminum hydroxide 20g Starch 5.0g 1.0g of field greens powder and 1.0g of glycerin Sr(NO ₃ ) ₂ 0.4g, Ca(NO ₃ ) ₂ ·4H ₂ O 0.7g and H ₃ PO ₄ 1.8g _HNO3 20% HNO ₃ 1% 45% 5h 10 700 Boehmite 30g Glucose 10.0g Citric acid 1.8g Mg(NO ₃ ) ₂ 6H ₂ O 1.5g HCl20% HNO ₃ 1% 45% 5h 11 800 Clay 20g Sucrose 7.0g Oxalic acid 3.5g Ca(NO ₃ ) ₂ ·4H ₂ O0.7g Malonic acid 30% HCl 0.8% 40% 5h

Example 12

Take 100 g of ZSM-5 sodium zeolite raw powder (SAR=1000), add 2.0 g of turnip powder and 2.0 g of starch into it, and mix the above raw materials evenly to form a mixture. 3.4g La(NO ₃ ) ₃ ·6H ₂ O was dissolved in 75g of 33.3% by mass silica sol solution to form a mixed solution. Slowly add this mixed solution into the above mixture, mix evenly, extrude into Φ2×5mm strips, dry at 80°C for 12 hours at a constant temperature in an air atmosphere, and calcinate at 600°C for 5 hours. According to the amount of liquid-solid ratio of 10mL HCl/1g zeolite, exchange 3 times with 4% HCl solution at 60° C. for 2 hours each time. Wash with deionized water and dry at 120°C to obtain H-ZSM-5 zeolite. The above-mentioned hydrogen-type zeolite was treated with H ₂ O/N ₂ gas with a H ₂ O volume percentage of 40% at 600°C for 8 hours, and the obtained catalyst was crushed, and the reaction was mixed with dimethyl ether and water (mass ratio CH ₃ OCH ₃ :H ₂ O=2:1), sieved out 20-40 mesh particles for activity evaluation, the catalyst activity evaluation results are shown in Table 3.

Example 13

2.0 g of glycerin was used instead of 2.0 g of scallop powder in Example 12, and 2.0 g of methyl cellulose was used as a pore structure modifier instead of 2.0 g of starch in Example 12. The rest of the preparation conditions were the same as in Example 12. The reaction was fed with mixed feed of dimethyl ether and water (mass ratio CH ₃ OCH ₃ :H ₂ O=2:1). The activity evaluation results of the catalyst are shown in Table 3.

Example 14

The 2% by mass ammonium nitrate solution was used instead of the 2% by mass HCl solution in Example 1 as the exchange solution, and the rest of the preparation conditions were the same as in Example 1. The reaction was fed with mixed feed of dimethyl ether and water (mass ratio CH ₃ OCH ₃ :H ₂ O=2:1). The activity evaluation results of the catalyst are shown in Table 3.

Example 15

A solution containing 2% ammonium chloride and 1% ammonium bicarbonate to replace the 2% ammonium nitrate solution in Example 14 as an exchange solution, and all the other preparation conditions were the same as in Example 14. . The reaction was fed with mixed feed of dimethyl ether and water (mass ratio CH ₃ OCH ₃ :H ₂ O=2:1). The activity evaluation results of the catalyst are shown in Table 3.

Catalyst intensity and reaction result of table 3 embodiment 2-13

2 86 5.6 44.9 14.0 100 3 106 11.5 42.1 13.2 99.6 4 82 6.6 43.4 14.6 100 5 70 6.4 43.2 15.8 100 6 62 8.6 40.4 14.7 98.9 7 74 6.6 44.7 15.8 100 8 88 5.7 44.4 13.8 100 9 62 8.2 42.7 15.2 99.8 10 64 3.9 40.3 14.3 97.5 11 98 8.1 43.1 12.3 100 12 48 9.5 45.4 10.4 99.8 13 54 9.4 42.0 8.5 100 14 67 6.9 44.0 9.9 100 15 71 8.4 43.9 12.6 100

^* is the sum of 1-butene, 2-butene and isobutene

Example 16

Comparative example 2, 3 and embodiment 1, 7, 8, 12 are used for the reaction that the mixed feed of methanol, dimethyl ether and water three is used for, wherein the mass ratio of methanol, dimethyl ether, water is 1 : 1: 1, the evaluation results are shown in Table 4.

Table 4 Methanol and dimethyl ether are converted into the reaction result of light olefin

catalyst Ethylene selectivity (%) Propylene selectivity (%) C ₄ ⁼ Selectivity ^* (%) Methanol conversion rate (%) when reacting for 200 hours DME conversion rate (%) when reacting for 200 hours Comparative example 2 7.2 40.5 16.3 99.5 99.9 Comparative example 3 6.8 42.5 13.4 99.0 99.2 Example 1 5.8 43.5 15.3 100 100

Example 7 7.5 41.7 14.7 100 100 Example 8 8.4 44.1 15.0 100 100 Example 12 9.4 42.8 13.4 99.1 99.4

^* is the sum of 1-butene, 2-butene and isobutene

Comparative example 1

Take 100g of ZSM-5 zeolite raw powder (SAR=200), add 25g of alumina, 2g of methyl cellulose and 3g of scallop powder to it, mix the above raw materials evenly, and adjust the liquid-solid ratio to 1.5mL of nitric acid/2g of zeolite The nitric acid solution with a mass percent content of 20% is slowly added to the above mixed raw materials, mixed evenly, extruded into φ2×5mm strips, dried at a constant temperature of 80°C for 12h, and calcined at 600°C for 5h in an air atmosphere to obtain the catalyst. For the precursor, the liquid-solid ratio is 10 mL HCl/1 g zeolite, and the catalyst precursor is exchanged with 2% HCl solution by mass percentage at 60° C. for 3 times, each time for 2 hours. Wash with deionized water and dry at 120°C to obtain H-ZSM-5 zeolite. The above-mentioned hydrogen-type zeolite was treated with a mixed gas of H ₂ O/N ₂ with a H ₂ O volume percentage of 50% at 550° C. for 8 hours to obtain a catalyst marked as B-1. B-1 was crushed, and 20-40 mesh particles were screened out for activity evaluation. The reaction was mixed with methanol and water (mass ratio CH ₃ OH:H ₂ O=2:1), and the catalyst activity evaluation results were as follows: Table 1 shows.

Comparative example 2

Dissolve 0.343g La(NO ₃ ) ₃ ·6H ₂ O in 10mL deionized water to make an impregnation solution. 10 g of catalyst B-1 prepared in Comparative Example 1 was impregnated at room temperature for 12 hours, dried at 80° C. for 12 hours, and calcined at 600° C. for 5 hours. The above-mentioned hydrogen-type zeolite was treated with H ₂ O/N ₂ gas with a volume percentage of H ₂ O of 50% at 550° C. for 8 hours. The catalyst obtained in this way contains 1% La in terms of mass percentage, the catalyst is marked as B-2, B-2 is broken, and 20-40 mesh particles are sieved for activity evaluation, and the reaction is mixed with methanol and water. Table ₁ shows the _catalyst activity evaluation results.

Comparative example 3

2×5mm条状，于80℃下恒温干燥12h，600℃煅烧5h得催化剂前躯体III；将催化剂前躯体III用H₂O体积百分含量为50％的H₂O/N₂气体于550℃下处理8h。得到的催化剂记为B-3，该催化剂以质量百分含量计含1％的La。将B-3进行破碎，筛分出20～40目的颗粒用于活性评价，反应以甲醇和水混合进料(质量比CH₃OH∶H₂O＝2∶1)，催化剂的活性评价结果如表1所示。催化剂的活性评价结果如表1所示。Take 100 g of ZSM-5 zeolite raw powder (SAR=200), and exchange it with 2% HCl solution by mass percentage for 3 times, each time for 2 hours, according to the liquid-solid ratio of 10 mL HCl/1 g zeolite. Wash with deionized water and dry at 120°C to obtain catalyst precursor I. Dissolve 3.4g La(NO ₃ ) ₃ ·6H ₂ O in 100mL deionized water to make an impregnation solution. The catalyst precursor I was impregnated at room temperature for 12 hours, dried at a constant temperature at 80°C for 12 hours, and calcined at 600°C for 5 hours to obtain the La-modified catalyst precursor II; then the catalyst precursor II was used for molding, and the steps were as follows: Add 25g of alumina, 2g of methylcellulose and 3g of turnip powder to the body II, mix the above raw materials evenly, and slowly add the nitric acid solution with a mass percentage of 20% according to the liquid-solid ratio of 1.5mL of nitric acid/2g of zeolite , mix well, squeeze into

2×5mm strips, dried at 80°C for 12 hours, and calcined at 600°C for 5 hours to _obtain catalyst precursor _{III ;} ℃ for 8h. The obtained catalyst is denoted as B-3, and the catalyst contains 1% La by mass percentage. B-3 was crushed, and 20-40 mesh particles were sieved for activity evaluation. Methanol and water were used as feed mixture for the reaction (mass ratio _CH3OH : _H2O =2:1), and the activity evaluation results of the catalyst were as follows: Table 1 shows. The results of catalyst activity evaluation are shown in Table 1.

Claims (12)

1. A molecular sieve catalyst for preparing low-carbon olefins, in parts by weight, said catalyst is made of raw materials comprising the following components: 30-93.7 parts of sodium type ZSM-5 zeolite, 5-40 parts of bonding agent, 0.1-10 parts of heteroelement modifier, 1-15 parts of pore structure modifier and 0.1-5 parts of extrusion aid, and the heteroelement modifier contains B, P, La, Ca , Mg, Sr, Zn, Cu, Mn, Cd, Ga and In soluble matter of one or several elements, preferably, in parts by weight, each component in the raw material is: 46-87.2 parts The sodium type ZSM-5 zeolite, 10-30 parts of binder, 0.5-5 parts of heteroelement modifier, 2-7 parts of pore structure regulator and 0.3-2 parts of extrusion aid. 2. The molecular sieve catalyst according to claim 1, wherein said sodium-type ZSM-5 zeolite is a sodium-type ZSM-5 zeolite with a silicon-aluminum molar ratio of 20-2000, preferably with a particle diameter of 0.1 mm or less and a silicon-aluminum molar ratio of 20-2000. Sodium ZSM-5 zeolite with a ratio of 200-1000. 3. The molecular sieve catalyst according to claim 1 or 2, wherein said binder is aluminum hydroxide, activated alumina, boehmite, pseudoboehmite, silica sol with a particle diameter below 0.1mm and one or more of clay, preferably one or more of activated alumina, pseudo-boehmite, silica sol and clay. 4. The molecular sieve catalyst according to any one of claims 1-3, wherein said pore structure regulator is selected from one of methyl cellulose, starch, polyvinyl alcohol, polyethylene glycol, sucrose and glucose One or more, preferably, the pore structure regulator is selected from one or more of methylcellulose, starch and sucrose. 5. The molecular sieve catalyst according to any one of claims 1-4, wherein said extrusion aid is selected from one of graphite powder, turnip powder, oxalic acid, tartaric acid, citric acid, glycerol and stearic acid or several kinds, preferably any two of turnip powder, citric acid and glycerin are an extrusion aid composed of 1:1 by mass ratio. 6. The molecular sieve catalyst according to any one of claims 1-5, wherein said heteroelement modifier is a soluble substance containing one or more elements in P, Mg, La, Mn and Zn . 7. A method for preparing the molecular sieve catalyst described in any one of claims 1-6, the method may further comprise the steps: a. mix sodium type ZSM-5 zeolite, pore structure regulator, extrusion aid, binder, heteroelement modifier and peptizer evenly; b. molding the mixture obtained in step a, drying, and calcining to obtain the precursor I of the catalyst; c. exchange the precursor I of the catalyst obtained in step b in 1) one or more solutions selected from hydrochloric acid, sulfuric acid and nitric acid or 2) an inorganic ammonium solution, and obtain the catalyst precursor II after drying; d. the catalyst precursor II obtained in step c is treated with water vapor and N ₂ mixed gas to obtain the catalyst, preferably, in the step a, at first the sodium type ZSM-5 zeolite and the pore structure are adjusted The agent and the extruding aid are mixed to obtain a mixture, and then the heteroelement modifier and the peptizing agent are added to the mixture. 8. The method according to claim 7, wherein the peptizer described in step a is selected from one or more of nitric acid, hydrochloric acid, phosphoric acid, sulfuric acid, formic acid, acetic acid and malonic acid, preferably, the The peptizer is selected from one or more of nitric acid, acetic acid and phosphoric acid. 9. The method according to claim 7 or 8, wherein when the binder in the step a is silica sol, the step a is to use sodium type ZSM-5 zeolite, pore structure regulator, extrusion aid The agent and the heteroelement modifier are mixed evenly. 10. The method according to any one of claims 7-9, wherein in said step b, the mixture obtained in step a is shaped, dried at 50-120°C, and calcined at 500-700°C in an air atmosphere 5-7 hours to obtain the precursor I of the catalyst, preferably, dry at 70-100°C, and calcinate at 550-650°C for 5-6 hours in an air atmosphere, more preferably, dry at a constant temperature of 80°C, and Calcined at 600° C. for 5 hours to obtain the precursor I of the catalyst. 11. according to the method described in any one in claim 7-10, wherein in described step c, the precursor I of the catalyst that step b obtains is in 1) mass percentage content be the selected one of 0.1-5%. One or more solutions in hydrochloric acid, sulfuric acid and nitric acid or 2) one or more solutions selected from ammonium nitrate, ammonium chloride and ammonium bicarbonate at 20- Exchange 2-5 times at 90°C for 1-6 hours each time, then wash the exchanged catalyst precursor I with deionized water, then dry the catalyst precursor I at 60-160°C to obtain catalyst precursor II ; Preferably, the precursor I of the catalyst obtained in step b is exchanged 3-4 times at 40-70 ° C for one or more solutions selected from hydrochloric acid, sulfuric acid and nitric acid at a mass percentage of 0.8-4% , each time for 2-5 hours, then wash the exchanged catalyst precursor I with deionized water, then dry the catalyst precursor I at 90-140°C to obtain the catalyst precursor II; more preferably, the step The precursor I of the catalyst that b obtains is that one or more solutions selected from hydrochloric acid, sulfuric acid and nitric acid are exchanged 3 times at 60 ℃ in the mass percent composition of 3%, and each time is 2 hours, then wash with deionized water The exchanged catalyst precursor I was then dried at 120° C. to obtain the catalyst precursor II. 12. according to the method described in any one in claim 7-11, wherein in described step d, water vapor and _N Mixed gas at 400-700 ℃, process 5-10 hour, and water vapor accounts for 30-70% of the volume of the mixed gas, preferably, in the step d, the mixed gas of water vapor and N ₂ is treated at 500-600°C for 5-8 hours, and the water vapor accounts for 40-70% of the volume of the mixed gas 60%, more preferably, in said step d, the mixed gas of water vapor and N ₂ is treated at 600°C for 8 hours, and the water vapor accounts for 50% of the volume of the mixed gas.